Method for recovering oil from oil shale



Aug- 28 1962 l.. D. FRIEDMAN Erm. 3,051,644

METHOD FCR RECOVERING OIL FROM OIL SHALE Filed July l, 1959 FII United States Patent O 3,051,644 METHGD FOR RECOVEG OIL FROM @EL SME Louis D. Friedman and Leon P. Gaucher, Beacon, N.

assiguors to Texaco Inc., New York, NX., a corporation of Delaware Filed July 1, 1959, Ser. No. 824,300 1 Claim. (Cl. 20S-11) This invention relates to an improved process for the recovery of oil from oil shale.

In carrying out the process of this invention, oil shale particles are subjected to treatment with steam at a pressure in the range of 1000 to 3000 pounds per square inch gauge and a temperature in the range of 700 to 900 F., for a period of time within the range of about 20 minutes to 6 hours. In a preferred operation, shale particles are mixed with suicient water to form a pumpable mixture and the mixture passed under pressure through an elongated heating zone of restricted cross-sectional area iu which the water is vaporized, entraining the shale particles in steam, and the mixture heated to the desired temperature; the heated mixture is discharged into a soaking zone of large volume wherein the oil shale is subjected to the stripping and heating action of steam for `the required period and from which recovered oil from the oil shale is withdrawn in vapor form admixed with said steam. Oil yields of more than 100 percent in comparison with the standard Fischer assay, are obtained from commercial grade oil shales. The quality of the recovered oil is comparable with that obtained by other methods of retorting.

It is known that kerogens contained in oil shale may be converted to hydrocarbon oil by the application of heat. Various methods have been proposed for the recovery of hydrocarbon oil from oil shales. For example, it has been proposed heretofore to recover shale oil from oil shale by contacting the shale with steam `at temperatures above 850 F. and at substantially atmospheric pressure. It has also been proposed to hydrate oil shales with liquid water at 500 to 700 F. under elevated pressures of the order of about 1,000 to about 3,000 pounds per square inch gauge.

The present process has a distinct advantage over such prior proposals. The yields of hydrocarbon oil are exceptionally high as compared With low pressure steam distillation operations of the prior art. As compared with hydration with water in liquid phase, the present process has the advantage of requiring very little process Water and of permitting the recovery of the shale oil directly. In the liquid phase hydration process, the clayey pulp resulting from hydration must be further treated, e.g. with ya hydrocarbon solvent, to recover the oil therefrom. Condensate water from the present process may be recirculated to the slurry feed preparation step. Relatively small amounts of make-up water are required. This is a denite advantage in arid regions, for example, the Western part of the United States where many commercial shale beds are located.

The process of this invention provides a method for direct recovery of oil in high yield from oil shales by retorting with steam at a pressure above 1,000 pounds per square inch gauge and at relatively low temperature in the range of 700 to 900 F. The relatively mild temperature employed in the present process largely prevents decomposition of carbonates contained in the shale. A large part of the heat required in conventional shale retorting processes is required for decomposition of carbonates. Carbon dioxide liberated from the carbonates generally serves no useful purpose in the retorting process.

The process of this invention will be more readily understood from the following detailed description, taken Mice in conjunction with the accompanying drawing. 'Ihe FIG- URE illustrates diagrammatically an arrangement of apparatus suitable for carrying out the present process.

With reference to the figure, oil shale crushed to a particle size not larger than about 1A inch diameter is charged to mixer 1 wherein it is admixed with suilicient water to form a pumpable mixture or slurry. A minimum of about 35 percent water by weight of the nal slurry is generally required; usually approximately equal parts of water and shale by weight are preferred.

We have found, as indicated in the examples hereinafter, that particles smaller than about 1A inch in average diameter are not particularly advantageous insofar as the recovery of she oil from the oil shale is concerned. Smaller particles are, however, somewhat more readily handled as a suspension or slurry and are preferred for this reason. Usually it is desirable to crush the oil shale only to the extent necessary to permit the shale particles to pass through a sieve or screen having openings of about 1A inch and to utilize the unclassified material passing through the screen as feed to the process.

To prevent the formation of scale in subsequent heating operations it is desirable to add an alkali metal hydroxide, preferably sodium hydroxide, to the slurry. An alkali metal carbonate may also be added to the slurry to supplement the action of alkali metal hydroxide. The preferred treatment involves addition of both alkali metal carbonate and alkali metal hydroxide. The amount of additive required to prevent scale formation in the heater will depend upon the chemical composition of the oil shale, but may be determined for any given shale by simple tests. Trouble free operation is obtained when the pH of the slurry is between 9 and 10, and the hardness, expressed as calcium carbonate, is between 0 and 2 parts per million.

To determine the amounts, for example, of sodium hydroxide and sodium carbonate, required to produce a slurry which will not cause scale deposits to form on heated surfaces, sodium hydroxide is added to the slurry until the pH is between 9 and l0. The hardness, expressed as calcium carbonate, is then determined and an amount of sodium carbonate added which is sutlcient to precipitate calcium remaining in the solution in the slurry water. The calcium is precipitated as insoluble calcium carbonate which is deposited on the solid shale particles and passes through the heating coil with `the solid particles without depositing on the walls of the tubular heater.

Slurry is withdrawn Ifrom mixer 1 to a pump 2 from which it is passed into and through the initial portion of a heater tube at a rate sufficient to prevent separation of the solid particles Afrom the aqueous carrier, generally at a linear velocity within the range of 1/2 to l0 feet per second, suitably about l to 2 feet per second. Heat may be supplied to the tube 3 from any suitable source, for

example, an oil-fired furnace 4. The slurry is heated in the initial or vaporizing section 3a of the tubularl heater by an amount at least suicient to vaporize the water to steam. When the water is vaporized from the moving stream of slurry, the resulting steam entra-ins the particles of solid shale in steam owiug at relatively high velocity, generally 4 to 50 feet per second, through a second portion, or high velocity section 3b, of the tubular heater 3. From the high velocity section of the heater, the dispersion is passed into a low velocity section 3c the heating coil containing tubing of langer diameter than that in said vaporizing and high velocity sections of the heater where the entrained shale is vfurther heated to a temperature in the range of 800 to l000 F.

The tubular heater can have any desired shape, such as single or double helical coils, parallel straight pipe lengths connected by return bends, sinusoidal or other suitable configuration, or even a long straight length of pipe. The various sections indicated, i.e. the vaporizing, high velocity, and low velocity sections, may be each located in one or more separate heating furnaces.

A The dispersion is discharged through line 8 into soaking z-one 9. The soaking zone is designed to maintain the shale in contact with steam from heater 4 for a period of time Within the range of about 20 minutes to about 3 hours. Some of the retorting or liberation of oil from the oil shale fby conversion of the kerogen in the oil Vshale to hydrocarbon oil is accomplishediin the heater and the remainder takes place in soaking zone 9. The soaking zone is maintained at a temperature within the range of about 700 to 900 F. Preferably the temperature in the soaking zone is in the range of 800 to 900 F. `and the residence time in :the coil and soaking zone of the individual shale particles is of the order of 30 minutes to 2 hours. Oil s-hale and steam are heated in the low velocity section of heater 4 to a temperature in the range of about 800 to 1,000 -F. sufficient to maintain the desired temperature in soaking zone 9. All of the heat required for distillation and stripping of the oil from the oil shale in soaking zone 9 is derived from heater 4.

The soaking zone or vessel 9 is designed so that the velocity of the steam upwardly through the particles of oil shale contained therein'is suflicient to impart some motion or jiggling to ftheshale oil particles contained therein without the violent agitation characteristic of uid bed reaction chambers and without substantial carryover of particles Ifrom the soaking zone. With shale particles ranging in size from a iine powder (smaller than 300 mesh) to particles .1A inch diameter, the linear superficial veloci-ty of steam in the soaking zone required to produce jiggling of the particles in the bed is generally within the range of `0.1 to 3.0 feet per second, usually 0.3 to 1.0 foot per second. The linear superficial velocity may be defined as the velocity which the gas, or in this case, steam, passing upwardly through the vessel lwould attain if lthere were no solids present in the vessel.

'Steam and oil vapors liberated 'from the oil shale in soaking zone 9 are discharged through line 11 to a separator 12. Vapors :from line 11 contain some solid particles entrained therein which are removed from the vapor stream by separator 12, suitably a cyclone'type separator.V

As illustrated the soaking zone is operated with a bed level somewhatrbelow thetop of the vessel and below outlet line 11 so that onlyv the finest particles of the oil shale are entrained in the vapors and discharged through line 11. Alternatively, and without departing `from the spir-it of this invention, the soaking zone may be operated completely iilled with solid particles so that all of residual solid is discharged through line 11 entrained in the vapor stream. In this latter case, all of the residue passes to separator 12 wherein it is separated from the steam and oil vapors.

'IThe solidY residue from separator 12 is discharged through line 13. The steam and oil vapors pass lthrough line 14 to a condenser 15 Where they are condensed and resulting condensate passed through line 16 to ya condensate receiver 17. In the condensate receiver, the oil yand water separate'into immiscible layers; oil is withdrawn lthrough line 18 and the water discharged through line 19.V VWater from line 19 may Vbe recirculated to mixer 1 for use in the preparation of slurry 4feed to the process.

Treated shale Withdrawn from the top of the bed in soaking zone 9 passes through line 21 to shale receiver 22. Water is introduced into shale receiver 22 through line 23 -to displace residual oil om the spent oil shale `and to assist in further handling of the residual shale under pressure. To lfacilitate the separation between the residual oil and water, it is preferable to introduce a light hydrocarbon suitably a hydrocarbon within .the distillate boiling range, eig. kerosene or gas oil, into contact with theV spent shale inline 21. The hydrocarbon is preferably added through line 2A. Line 26 permits gases displaced lfrom the spent shale in shale receiver 22 to return to the `soaking zone and discharge through line 11.

The mixture of oil, water and shale from receiver 22, maintained at elevated pressure, is `discharged into a separator 31 wherein the hydrocarbon is separated from the Water and residual solids. As illustrated in the drawings, the residual solid suspended in liquid is discharged from receiver 2 2 through valve 27 into a lock hopper 28 from which the'liquid-solid mixture is discharged through valve 29 to separator 31. Separator 31 may be `at substantially atmospheric pressure.Y By alternately opening and closing valves Z7 Iand 29, shale may be removed from the high pressure shale receiver 22 without `danger of permitting steam and gases to escape. In separator 31, the oil and water `form immiscible layers, the shale residue remaining in the water layer. Oil from the shale, together with added hydrocarbon, is withdrawn from separator 31 through line 32, while the water and residual shale particles are discharged through line 33.

The process of this invention is further illustrated in the following examples reporting )data from runs demonstrating the eiect of steam at high pressures on shale oil recovery.

Colorado oil `shale having a Fischer yassay of 28.3 gallons per ton was crushed to a particle size smaller than 1A inch and treated with steam at a temperature and pressure as indicated. The results of these tests in cornparison with the standard Fischer assay are shown in the following table. The standard Fischer assay method is described in U.S. Bureau of Mines, Rl. 3977 (October 1946). Gas `analysis is reported in volume percent, o1' mol percent, on a water-free and air-free basis. Oil analysis is in weight percent.

Fischer Example Example Assay 1 2 Tem F 32 700 900 Time, hrs-- 1 6 1-6 Pressure, p. 0 3, 000 3, OOO Percent Organic Removedb 84.2 84.5 86.2 Percent Carbon Removed 55. 6 69. 7 61.9 Percent Organic Carbon Removed 80. 3 85.7 83.2 Gas Analysis:

Hydrogen- 3. 8 Methane 4.1 C2 Hydrocarbons 1. 3 Cri-Hydrocarbons 2. 1 Carbon dioxide 81. 6 Nitrogen and Argon 6. 6 Hydrogen sulde- 0. 5 Oil Analysis:

Total heating time. b Includes nitrogen, sulfur and oxygen. No appreciable time effect observed after 1 hour at 900 F.

Obviously, many modications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit andY scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claim.

VWe claim: d Y

A method for recovery of oil Vfrom oil shale which comprises forming a owable mixture of particlesof oil shalelin Water, introducing said, mixture as a ilowing stream at a velocity in the range ofl to l0 feet per second toran elongated tubular heating zone at a pressure above about 1000 pounds per square inch gauge, heating said mixture in Vsaidrheating zone as it ows therethrough wardly through said soaking zone in contact with said shale particles in said bed at a velocity sucient to impart motion to said shale particles contained therein but insuicient to produce a fluid bed of said particles in said zone, maintaining said particles in said bed in Contact with steam at a pressure Within the range of 1000 to 3000 pounds per square inch gauge and a temperature within the range of 800 to 900 F. for a period of 20 minutes to 3 hours, continuously removing treated shale particles References Cited in the le of this patent from the uppermost portion of said bed, withdrawing 10 2,911,349

steam and oil vapors substantially free from shale particles from said soaking zone at a point above the uppermost portion of said bed, and recovering oil from said eiuent stream of steam and oil vapors.

UNITED STATES PATENTS Hacksta Mar. 11, 1924 Coogan Mar. 18, 1924 Truitt et al. Jan. 5, 1954 Stewart et al Nov. 27, 1956 Rees May 21, 1957 Stewart et al. Aug. 12, 1958 Coulson Nov. 3, 1959 FOREIGN PATENTS Canada July 27, 1948 

